Hydraulic actuator with load proportional locking means



April 11, 1961 H. M. GEYER HYDRAULIC ACTUATOR WITH LOAD PROPORTIONALLOCKING MEANS 3 Sheets-Sheet 1 Filed Feb. 18, 1959 INVENTOR. Howard M.Geyer arm His Attorney April 11, 1961 H. M. GEYER 2,979,034

HYDRAULIC ACTUATOR WITH LOAD PROPORTIONAL LOCKING MEANS Filed Feb. 18.1959 3 Sheets-Sheet 2 INVENTOR. Howard M. Geyer His Attorney April 11,1961 H. M. GEYER 2,979,034

HYDRAULIC ACTUATOR WITH LOAD PROPORTIONAL LOCKING MEANS Filed Feb; 18.1959 3 Sheets-Sheet 3 INVENTOR. Howard M. Ge yer BY 44. a $34 HisAttorney ite- States HYDRAULIC ACTUATOR WITH LOAD PROPOR- TIONAL LOCKINGMEANS Filed Feb. 18, 1959, Ser. No. 794,112

20 Claims. (Cl. 1211-40) This invention pertains to .fiuid pressureoperated actuators, and particularly to a linear actuator havingbidirectional load sensitive locking means.

Heretofore, actuators have been designed including unidirectional loadsensitive locking means of the manually engageable type, for preventingactuator movement in one direction dueto external loading. An actuatorof this type is shown in my Patent 2,859,640. In addition, actuatorshave been designed wherein the unidirectional load sensitive lockingmeans are automatically released by servo mechanism simultaneously withthe application of pressure fluid to the actuator cylinder in oppositionto the external load, such an actuator being shown in copendingapplication Serial No. 551,801, filed December 8, 1955, in the name ofHoward M. Geyer et al. and assigned to the assignee of this invention,now Patent No. 2,879,746. The present invention relates to an actuatorconstruction including load sensitive bidirectional locking means whichcan be released by either a servo mechanical or manual means, togetherwith an inching control system for controlling the rate of actuatormovement.

Accordingly, among my objectsare the provision of an actuator assemblyincluding bidirectional load sensitive locking means; the furtherprovision of an actuator assembly including bidirectional load sensitivelocking means and servo means for releasing the locking means; thefurther provision of an actuator assembly of the aforesaid typeincluding manual means for releasing the bidirectional locking means;and the still further provision of a control system for an actuator ofthe aforesaid type including means for controlling the rate of actuatormovement by controllin the pressure -in the servo actuated loci:releasing means.

The aforementioned and other objects are accomplished in the presentinvention by incorporating a rotatable and axially movable worm shaftassembly which carries a pair of friction locking elements that areengageable with brake surfaces so as to lock the actuator againstmovement in both directions due to external loading of the actuator.Since the braking force of the locking means is proportional to theload, the locking means operate as a selfenergizing brake. Specifically,the actuator includes a cylinder having .a reciprocable piston disposedtherein capable of fluid pressure actuation in both directions. The

piston divides the cylinder into an extend chamber and a retractchamber, and includes an extending rod portion adapted for connection toany suitable load device. The

piston, by virtue of its connection to the load device, is.

restrained against rotation, and carries a nut. The nutthreadedlyrengages a reversible Acme serewthat is'rotatably journalledwithin the cylinder. Accordingly, it'is apparent that pistonreciprocation is dependent upon and effects rotation of the screwshaft,andtherefore'if rotation of the screw shaft is prevented, the actuatorpiston wilhhe locked against movement."

The locking 'me'aasanupae the rotatable and axially movable wor'm shaftalluded foher'einbfdr'e, the worm portion'o'f 'which meshes with n wormwheel attached to 2,979,034 Patented Apr. 11, 1961 the screw shaft. Theworm shaft assembly includes a pair of spaced flanges, or collars,constituting friction brakes, the outer surfaces of which are engageablewith shoulders of the actuator cylinder assembly. The worm shaft isbearing mounted adjacent its end within the actuator cylinder. The outerraces of the bearing for totatably journalling the worm shaft assemblywith the cylinder are connected to brake release pistons disposed withinbrake release cylinders in the cylinder assembly.

Eachvbrake releasing cylinder is connected to a con duitthrough whichfluid under pressure is supplied to one of the actuator chambers. Thesupply and drain of fluid under pressure to the actuator chambers iscontrolledby a four-way valve. Accordingly, whenever fluid under apressure potential suflicient to exceed the external load is applied toanactuator chamberin opposition to the external load, the load on theworm shaft assembly will be removed by the pressure in the actuatorchamber.

To control the .rate of actuator movement when the actuator isexternally loaded, either in tension or compression, the pressurepotential of the operating fluid is slowly increased so as to relievethe locking means propor- A ternal load, when the braking force of thelocking means has been reduced so that the brake torque is less thanthat necessary to restrain the worm shaft assembly against rotation, theactuator will begin to move. Thus, by controlling the lock releasingpressure, the rate at which the actuatormoves can be regulated.

Ina modified embodiment, the brake releasing cylinders embody manuallyoperable screw devices whichcan engage the lock releasing pistons so asto center the worm shaft assembly in the absence of fluid pressureapplication to the lock releasing cylinders. Y

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein preferred embodiments of the present invention areclearly shown, and wherein like numerals denote like parts throughoutthe several views. V i V V In the drawings:

Figure l is a perspective view, partly in section and partly inelevation, depicting an actuator constructedaccording to one embodimentof the present invention,

Figure 2 is a view similar to Figurel with the locking means engaged dueto a tension load.

Figure 3 is a transverse sectional view of the actuator locking means.

Figure 4 is a schematic view of the novel actuator control system of thepresent invention. i

Figure 5 is a sectional View, depicting a modifiedactuator construction.V I

With particular reference to Figure 1, an actuator is shown including acylinder it! having disposed thereip a reciprocable piston 12. Thepiston 12 divides the actuatorcylinder into an extend chamber ll andaretract chamber 136. One end of the cylinder 10 is closed by a head capassembly 13 connected thereto by a screw threaded coupling, the otherend of the cylinder 10 being closed by a tail cap 26, likewise connectedtheretob y'a screw threaded coupling. The piston 12 includes sealingmeansfizengageable with the'in nerperiphery of the cylinder 1% and''also includeswan integral axially extending movement thereof.

The piston 24 isthreacledly connected toanut 26, such r I that the nut26 reciprocates with the piston 12. An Acme screw shaft, or member, 28is rotatably journalled within the head cap assembly 18 of the actuatorby ball bearing means 30. A worm wheel 32 is rigidly attached to theinner end of the Acme screw shaft 26 within the head cap assembly 18.Since the piston 12 carries the nut 26, reciprocation of the piston 12is dependent upon and effects rotation of the screw shaft 28. Moreover,since the worm wheel 32 is rigidly connected to the screw shaft 28,rotation of the screw shaft will impart rotation to the worm gear.

With reference to Figures 1 and 3, a worm shaft assembly 34, the axis ofwhich is transverse to the axis of the screw shaft 28, is rotatablyjournalled within the head cap assembly 18 by ball bearing assemblies 36and 38. The worm shaft assembly includes a worm 40 meshing with the wormwheel 32 and a pair of spaced thrust 001- lars 42 and 44. The Worm andworm wheel are reversible, that is, during rotation of the worm wheel 32in the clockwise direction as viewed in Figure l, the worm shaftassembly 34 will rotate in the clockwise direction, and during rotationof the worm wheel 32 in the counter clockwise direction as viewed inFigure 1, the worm shaft assembly 34 will rotate in the counterclockwisedirection. Obviously, if the worm shaft assembly 34 is restrainedagainst rotation, the worm wheel 32 cannot rotate, and hence the screwshaft 26 cannot rotate and the piston 12 cannot reciprocate.

With particular reference to Figure 3, the thrust collar 42 has abraking surface 46 engageable with surface 48 of a shoulder integralwith a head cap assembly 18. The thrust collar 44 has a braking surface50 engageable with a surface 52 of the shoulder integral with the headcap assembly 18. Counterclockwise rotation of the worm wheel 32 exertsan axial thrust on the worm shaft assembly 34 to the left as viewed inFigure 3, thereby tending to urge the braking surface 50 and the thrustcollar 44 into engagemnet with the surface 52. Conversely, rotation ofthe worm wheel 32 in the clockwise direction exerts an axial thrust onthe worm shaft assembly 34 to the right thereby tending to move thebraking surface 46 of the collar 42 into engagement with the surface 48.Since the worm wheel 32 moves in the counterclockwise direction duringextending movement of the piston, the thrust collar 44 constitutes theextend locking means, and the thrust collar 42 constitutes the retractlocking means.

The outer race of the bearing 36, which is of the combined thrust andradial type, is carn'ed by an annulus 54 having an integral rod portion56 with a threaded end 58. The threaded end 58 is attached to a lockrelease piston 60 disposed within a lock release cylinder 62. Thecylinder 62 communicates with a lock release port 64.

Similarly, the outer race of the combined thrust and radial bearing 38is carried by an annulus 66 having an integral rod projection 68 with athreaded end 70, the threaded end 70 being connected-to a lock releasepiston 72 disposed within a cylinder 74. The cylinder 74 is connected toa lock release port 76. If both of the cylinders 62 and 74 are subjectedto hydraulic fluid under pressure, the worm shaft assembly 34 will becentered through the bearing assemblies 36 and 38 as depicted in Figure3, in which position the bidirectional locking means are released. Thecylinders 62 and 74 and the pistons 60 and 72, respectively, constituteservo means for releasing the locking means. that is, neither the extendlocking collar 44nor the retract locking collar 42 engages its brakingsurface 52 or 48, respectively. However, if neither lock releasecylinder 62 or 74 is subjected to fluid under pressure, and the actuatoris externally loaded, the worm shaft assembly will be moved axially toeither theleft or the right depending upon the direction of the load.Thus, for a tension load, as depicted in Figure2,

.the, worm shaft assembly 34 w ill move axially downward so thatthesurface 50 of the collar 44 engages the surface 52. The brake torque isdirectly proportional to the load, and since the area of the surfaces 50and 52 in engagement with each other results in a braking torque thatexceeds the torque due to the tension load, the actuator will be lockedagainst movement. Conversely, if the actuator is subjected to acompression load, the worm shaft assembly 34 will move axially upward sothat the surface 46 of the collar 42 engages the'surface 48. The brakingtorque for locking the actuator against a compression load is likewisedirectly proportional to the applied load.

With particular reference to Figure 4, the control system for theactuator will be described. The control system includes a four-way valvecomp-rising a reciprocable plunger 82 disposed for movement within avalve casing 84. The plunger 82 is formed with spaced lands, 86, 88, 9t)and 2, annular grooves 94, 96 and 98 being formed by the lands. Thevalve plunger 82 includes a rod portion 100 constituting a handle formanual operation.

The valve casing 84 is formed with an inlet port 102, a pair of controlports 104 and 106 and a pair of drain ports 108 and 110. The inlet port102 is connected to a suitable source of hydraulic fluid under pressure,not shown, such as a pump. The drain ports 108 and 110 are connected toa drain conduit 112. The control port 104 is connected to an extendconduit 114 and the control port 106 is connected to retract conduit116, the conduits 114 and 116 communicating with actuator ports 118 and120, and to brake ports 76 and 64.

The lauds 88 and 90 cooperate with control ports 104 and 106,respectively such that when the plunger 82 is moved upwardly, as viewedin Figure 4, the port 106 will be connected to the pressure supply port102 while the port 104 is connected to drain. Conversely, when theplunger 82 is moved downwardly, as viewed in Figure 4, the control port104 is connected to the pressure supply port 112 and the control port106 is connected to drain.

In the neutral position of the valve plunger 82, as depicted in Figure4, both of the control ports 104 and 106 are connected to drain, andhence the brake release cylinders 62 and 74 are not subjected topressure, whereupon if the actuator is subjected to an external load,the worm shaft assembly 34 will be moved axially in one direction or theother so as to lock the actuator piston against movement.

Assuming that the actuator is subjected to an external compression load,and is to be retracted, the valve plunger 82 is moved upwardly, asviewed in Figure 4, to connect port 106 to pressure port 102 and connectport 104 to drain. Accordingly, the brake release cylinder 62 will besubjected to pressure, the potential of which is determined by thedegree of opening of the port 106 to the pressure port 102. When thepressure potential of the fluid supplied to the brake release cylinder62 exceeds the external compression load, the worm shaft assembly,constituting the locking means, will be centered thereby permitting theactuator piston to be retracted. If the control valve plunger 82 ismoved'slowly upward from the neutral position with a compression load,as viewed in Figure 4, the brake release pressure is slowly increased soas to relieve the braking torque proportional to the brake releasepressure. When the-braking torque is less than that necessary torestrain the worm shaft against rotation the actuator begins to retract,so that by controlling the brake release pressure by throttling the flowthrough the control ports the rate at which the actuator piston movescan be regulated, and this type of operation is termed inching."

, Assuming that the actuator piston is subjected to an external tensionload, if the actuator is to be extended the brake releasing pressure incylinder 74 must exceed the brake torque imposed on the worm shaftassembly by the tension load. When the braking torque has been reducedtoa value less than: that necessary to restrain rotation of the worm shaftassembly, the actuator piston will be extended at a rate determined bythe flow of fluid to the control valve assembly. I

To efiect retract movement of the actuator under tension load, thecontrol valve plunger 82 is moved upwardly so as to connect port 1% topressure and connect port 104 to drain. The pressure in the retractchamber removes the load from the worm shaft assembly. If the actuatoris subjected to compression load, the application of pressure to theextend chamber removes the load from the worm shaft assembly so as torelease the locking means.

With reference to Figure 5, a modified actuator assembly is shownwherein each end wall of the brake releasing cylinders 62 and 74 has athreaded opening, 130 and 132 respectively. The threaded openings 130and 132 receive threaded lock releasing members 134 andl36,respectively, having knurled external heads 138 and 140. in the modifiedembodiment, the worm shaft assembly 34 can be manually centered byproper adjustment of the threaded brake releasing members 134 and 136.As depicted in Figure 5, the manual lock releasing means are used incombination with the hydraulic lock releasing means so as to facilitatemovement of the actuator due to external loads, if necessary, uponfailure of the fluid pressure system.

While the embodiments of the invention as herein disclosed constitutepreferred forms, it is to be understood that other forms might beadopted.

What is claimed is as follows:

1. An actuator assembly including, a cylinder, a reciprocable pistondisposed in said cylinder, a member rotatably journalled in saidcylinder and operatively connected to the piston such that pistonmovement is dependent upon and effects rotation of said member, andself-engageable, bidirectional, load sensitive locking means operativelyconnected with said member for preventing rotation thereof in eitherdirection so as to prevent movement of said piston in either directiondue to an external load.

2. An actuator assembly including, a cylinder, a reciprocable pistontherein, a member rotatably journalled in said cylinder and operativelyconnected to the piston such that piston movement is dependent upon andeffects rotation of said member, and releasable, self-engageable,bidirectional, load sensitive locking means operatively connected withsaid member for preventing rotation thereof in either direction so as toprevent movement of said piston in either direction due to an externalload.

3. An actuator assembly including, a cylinder, a reciprocable pistontherein, a member rotatably journalled in said cylinder and operativelyconnected to the piston such that piston movement is dependent upon andeffects rotation of said member, self-engageable, bidirectional, loadsensitive locking means operatively connected with said member forpreventing rotation thereof in either direction so as to preventmovement of said piston in either direction due to an external load, andservo means en gageable with said locking means to release said lockingmeans to permit movement of said piston in either direction.

4. An actuator assembly including a cylinder, a reciprocable pistondisposed therein, a member rotatably journalled insaid cylinder andoperatively connected to the piston such that piston movement isdependent upon and effects rotation of said member, self-engageable,bidirectional, load sensitive locking means operatively con nected withsaid member for preventing rotation thereof in either direction so as toprevent movement of said piston in either direction due to an externalload, and manual means engageable with said locking means to releasesaid locking means to permit movement of said piston in eitherdirection.

5. An actuator assembly including, a cylinder, at piston reciprocabletherein, a screw shaft rotatably journalled in said cylinder andoperatively connected to the piston aeraoss d v such that pistonmovement is dependent upon and effects rotation of said screw shaft,said screw shaft being restrained against axial movement relative to thecylinder,

and self-engageable, bidirectional, load sensitive locking meansoperatively connected with said screw shaft for preventing rotationthereof in either direction so as to prevent movement of said piston ineither direction due to an external load.

6. Self-engageable, bidirectional, load sensitive locking means for anactuator having a cylinder, a reciprocable piston disposed in saidcylinder capable of fluid pressure actuation in both directions, and amember rotatably supported in said cylinder and operatively connectedwith said piston such that piston movement is dependent upon and effectsrotation of said member, including, a rotatable and axially movableassembly engaging said member whereby rotation of said member in eitherdirection will eifect axial movement of said assembly in one direc-'tion or the other, said assembly including a pair of spaced thrustcollars, and a pair of spaced braking surfaces of said cylinderengageable with said thrust collars when said assembly is moved axiallyin either direction from a centered position for preventing rotation ofsaid assembly and said member in either direction to prevent movement ofsaid piston in either direction due to an external load.

7. Self-engageable, bidirectional, load sensitive locking means for anactuator having a cylinder, a reciprocable piston disposed in saidcylinder capable of fluid pressure actuation in both directions, and amember ro tatably supported in said cylinder and operatively connectedwith said piston such that piston movement is dependent upon and effectsrotation of said member, including, a rotatable and axially movableelement engaging said member, the axis of said element being transverseto the axis of said member whereby rotation of said member in eitherdirection will effect axial movement 'of said element in one directionor the other, a pair of spaced thrust collars attached to said element,a brake surface on said cylinder engageable with said thrust collarswhen said element is moved axially in either direction from a centeredposition for preventing rotation of said element and said member toprevent movement of said piston in either direction due to an externalload.

8. Self-engageable, bidirectional, load sensitive locking means for anactuator having a cylinder, a reciprocable piston disposed in saidcylinder capable of iluid pressure actuation in both directions, and amember rotatably supported in said cylinder and operatively connectedwith said piston such that piston movement is dependent upon and effectsrotation of said member, including, a worm gear connected to rotate withsaid member, a worm shaft engageable with said worm gear, said wormshaft being supported for rotation and'axial movement relative to saidcylinder whereby upon rotation of said member said worm shaft will moveaxially in one direction or the other, a pair of spaced thrust collarsattached to said worm shaft, and a cooperable braking surface of saidcylinder engageable with each of said thrust collars upon axial movementof said worm shaft in either direction from a centered position toprevent rotation of said worm shaft and said worm gear to therebyprevent movement of said piston in either direction due to an externalload.

9. The locking meansset forth in claim 8 including a pair of spacedcombined thrust and radial bearing assemblies for supporting said wormshaft.

10. The locking means set forth in claim 9 wherein each of said bearingassemblies includes inner and outer race members, and wherein the outerrace member of inder capable of fluidpressure actuation in eitherdirection, a member rotatably supported in the cylinder and operativelyconnected to the piston such that piston movement effects and is.dependent upon rotation. of said member, a rotatable and axially movableelement engaging said member, and self-engaging, bidirectional, loadsensitive locking means cooperable between said element and saidcylinder for locking the element and the member against rotation ineither direction to thereby lock the piston against movement in eitherdirection due to an external load.

12. A fluid pressure operated actuator including, a cylinder, areciprocable piston disposed in the cylinder capable of fluid pressureactuation in either direction, a member rotatably supported in thecylinder and operatively connected to the piston such that pistonmovement effects and is dependent upon rotation of said member, andreleasable self-engageable, bidirectional, load sensitive locking meanscooperable between said element and said cylinder for locking theelement and the member against rotation in either direction to therebylock said piston against movement in either direction due to an externalload.

13. The actuator set forth in claim 12 including servo means engageablewith said locking means for releasing said locking means.

14. The actuator set forth in claim 12 includingmanual means engageablewith said locking means for re leasing said locking means.

15. A fluid pressure operated actuator including, a cylinder, areciprocable piston disposed in said cylinder capable of fluid pressureactuation in both directions, a member rotatably supported in saidcylinder and operatively connected to the piston such that pistonmovement effects and is dependent upon rotation of said member, a wormgear attached to rotate with said member, brake means including a wormshaft engaging said worm gear,

means supporting said worm shaft for rotation and axial movementrelative to said cylinder, a pair of spaced thrust collars attached tosaid worm shaft, and a pair of spaced surfaces of said cylinderengageable with said thrust collars upon axial movement of said wormshaft in opposite directions from a centered position for restrainingrotation of said worm shaft and said member in proportion to an externalload acting in either direction on said piston.

means for supporting said worm shaft for rotation and axial movementcomprises a pair of spaced combined radial and thrust bearingassemblies.

17. The actuator set forth in claim 16 wherein said bearing assemblyincludes inner and outer races and wherein theouter race of each bearingassembly is carried by a reciprocable annulus whereby said brake meanscan be released to permit movement of the actuator piston in eitherdirection by centering said worm shaft through said annuli.

18. The actuator set forth in claim 15 including a pair of fluidpressure operated brake releasing pistons for centering said worm shaftto release said brake means.

19. The actuator set forth in claim 15 including a pair of manuallyoperable screw devices for centering said worm shaft to release saidbrake means.

20. A control system for a fluid pressure operated actuator having acylinder, a reciprocable piston disposed therein, a member rotatablyjournalled in the cylinder and operatively connected to the piston suchthat piston movement is dependent upon and effects rotation of saidmember, self-engageable, bidirectional, load sensitive locking meansoperatively connected with said member for preventing rotation thereofin either direction so as to prevent movement of said piston in eitherdirection due to an external load, and fluid pressure operated means forreleasing said locking means, including, a source of fluid underpressure, and manually operable throttle valve means for controlling theapplication of pressure fluid to the loci; releasing means and to theactuator cylinder whereby the rate of movement of said actuator pistoncan be regulated by controlling the pressure potential of the fluidapplied to the lock releasing means. I

References Cited in the file of this patent UNITED STATES PATENTS2,442,577 Ashton June 1, 1948 2,688,227 Geyer Sept. 7, 1954 2,705,939Geyer Apr. 12, 1955 2,859,640 Geyer Nov. 11, 1958 2,879,746 Geyer et al.Mar. 31, 1959 2,891,380 Geyer et al. June 23, 1959 2,927,556 Cain et a1Mar. 8, 1960

